This invention relates to vaccines for bacterial toxins from Bacillus anthracis. 
Anthrax is a disease cause by the sporulating bacteria Bacillus anthracis. Humans working with animal products are at risk from contracting anthrax. Areas such as Iran, Turkey, Iraq, Pakistan, and sub-Saharan Africa are hyperendemic for anthrax, although the organism can be found in most areas of the world. Anthrax manifests disease in three different ways. Inhalation, gastrointestinal, and cutaneous anthrax result from inhaling spores, ingesting spores in contaminated meat, or contacting spores in an open wound, respectively. Untreated inhalation or gastrointestinal anthrax has a case fatality rate of essentially 100 percent while cutaneous anthrax has a case fatality rate of up to 25 percent. Previous research has shown that the protective antigen (PA) produced by B. anthracis can protect mice from anthrax. Even though the Anthrax vaccine is FDA licensed, reactogenicity is mild to moderate.
Therefore, there is a need for an efficacious vaccine for anthrax useful for protecting humans.
The present invention satisfies the need discussed above. The present invention relates to a method and composition for use in inducing an immune response which is protective against infection with anthrax.
In this vaccine strategy, a gene coding for a protein of interest is cloned into a VEE virus vector in place of the VEE virus structural genes; the result is a self-replicating RNA molecule, a replicon, that encodes its own replicase and transcriptase functions, and in addition makes abundant quantities of mRNA encoding the foreign protein. When replicon RNA is transfected into eukaryotic cells along with two helper RNAs that express the VEE structural proteins (glycoproteins and nucleocapsid), the replicon RNA is packaged into VEE virus-like particles by the VEE virus structural proteins, which are provided in trans. Since the helper RNAs lack packaging signals neccessary for further propagation, the resulting VEE replicon particles (VRPs) which are produced are infectious for one cycle but are defective thereafter. Upon infection of an individual cell with a VRP, an abortive infection occurs in which the infected cell produces the protein of interest in abundance, is ultimately killed by the infection, but does not produce any viral progeny (Pushko et al., 1997, Virology 239, 389-401).
The PA gene which contains a prokaryotic secretory signal and the entire 83 kDa coding sequence (Welkos et al., 1988, Gene 69, 287-300), was inserted into the VEE replicon vaccine vector (FIG. 1) and have demonstrated high level expression of this bacterial protein in eukaryotic cells in culture. Mice, either the C57BL/6 strain or the A/J strain, inoculated with VRP containing the PA-replicon produced high specific antibody titers and were protected from developing anthrax when challenged subcutaneously with B. anthracis. 
Therefore, it is one object of the present invention to provide a VEE virus replicon vector comprising a VEE virus replicon and DNA fragments encoding the PA protein from B. anthracis. 
It is another object of the present invention to provide a self replicating RNA comprising the VEE virus replicon and any of the B. anthracis fragments described above.
It is another object of the present invention to provide infectious VEE virus replicon particles produced from the VEE virus replicon RNA described above.
It is further an object of the invention to provide an immunological composition for the protection of mammals against B. anthracis infection comprising VEE virus replicon particles containing any of the B. anthracis fragments described above or a combination of different VEE virus replicons each having a different B. anthracis fragment.